This proposal is comprised of clinical and experimental studies which expand the present understanding of fever in humans. The project is focused on the production and consequences of the polypeptide mediator of fever, leukocytic pyrgen (LP). The mechanism which signals human moncytes to begin synthesizing LP will be studied using a soluble, endogenously produced lymphokine, released in mixed leukocyte reactions. The characterization and mechanism of action of this pyrogen-inducing lymphokine will be investigated and are intended to elucidate cellular mechanisms in the production of immunologically mediated fever in humans. Using a radioimmunossay, several studies are designed to detect circulating LP in experimentally induced fever in normal volunteers as well as patients with febrile and non-febrile diseases. These clinical studies employ endotoxin and etiocholanolone as pyrogenic agents in humans; in addition, thses studies will be compared to a group of patients and volunteers receiving hyperthermia as part of a cancer therapy program. Studies will also be carried-out on the ability of human LP to enhance murine thymocyte blastogenesis, increase fibroblast proliferation and induce the synthesis of acute phase proteins. Aspects of these experiments will include the use of receptor binding inhibition, prostaglandin analyses, inhibitors of the cyclooxygenase and lipoxygenase pathways in order to study the mechanism of action of LP. Comparable experiments are also planned using brain slices incubated in vitro to ascertain the mechanism by which LP induces neurotransmitter and neuropeptide release or synthesis. Thus, these in vitro experiments intend to define a basic cellular mechanism by which LP mediates fever as well as certain parameters of the acute phase response. Because the studies depend on large amounts of purified LP, methods of improved production and recovery will be evaluated, including the production of monoclonal antibodies to human LP. Finally, considerable effort will be focused on determining the amino acid sequence of human LP. This undertaking is now feasible and knowledge of the amino-terminus sequence will confirm the purity of the pyrogen. In addition, knowledge of the active site sequence will provide a basis for design of therapeutic agents directed against the activity of this molecule.